Heme maintains catalytically active structure of cytochrome P-450.
Treatment of purified cytochrome P-450 LM2 and its liposome-bound form with hydrogen peroxide led to complete destruction of the P-450 heme. The apoenzyme thus produced could be reconstituted to catalytically active cytochrome P-450 by incubation with hemin, the reconstitution efficiency being 50% for the soluble enzyme and 80% for the liposome-bound enzyme. The removal of heme from the soluble hemoprotein resulted in a 3-fold decrease in the efficiency of its incorporation into sonicated liposomes. The contents of 5 secondary structure forms in the native, apo- and reconstituted holoenzymes were estimated from their circular dichroism spectra. It was thus found that the helix content increased from 34% to 60% upon removal of the heme from the native enzyme. We suggest that the increase in the helix content leads to a reduction of the incorporation efficiency into liposomal membranes.
Uvarov VYu
2nd Moscow Medical Institute, Department of Biochemistry, USSR.
Tretiakov
V E
VE
Archakov
A I
AI
D000818:Animals; D001051:Apoenzymes / Q000096:biosynthesis; D002384:Catalysis; D002942:Circular Dichroism; D065607:Cytochrome P-450 Enzyme Inhibitors; D004795:Enzyme Stability; D006418:Heme / Q000302:isolation & purification / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D011487:Protein Conformation; D011817:Rabbits; D013329:Structure-Activity Relationship
D001051:Apoenzymes; D065607:Cytochrome P-450 Enzyme Inhibitors; D006418:Heme; D006861:Hydrogen Peroxide